Cardiac stimulator lead with fluid restriction

ABSTRACT

A cardiac stimulator lead is provided that includes a connector for connecting to a cardiac stimulator and a tubular insulating sleeve that has a first end coupled to the connector and a second end. An electrode is coupled to the second end and has a longitudinal bore. An extendable/retractable corkscrew is positioned in the bore. In one aspect, the lead includes a radiopaque member moveable with the corkscrew to verify axial movement. In another aspect, the bore is configured so that the corkscrew will not extend fully unless tissue is present to engage the corkscrew. In another aspect, a shape-memory polymeric washer is included to restrict fluid influx after corkscrew deployment.

RELATED APPLICATIONS

This application is a division of U.S. Ser. No. 09/109,498 filed Jul. 2,1998, now U.S. Pat. No. 6,108,582, the specification of which is herebyincorporated by reference. This application is also related toApplicant's application entitled “Cardiac Stimulator Lead with Two-StageExtendable/Retractable Fixation”, U.S. Ser. No. 09/584,642, filed evendate herewith, now U.S. Pat. No. 6,181,500, which is incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to cardiac stimulator leads, and moreparticularly to a cardiac stimulator lead having an extendable andretractable screw-in fixation mechanism.

2. Description of the Related Art

Conventional cardiac stimulator systems consist of a cardiac stimulatorand an elongated flexible cardiac lead that is connected proximally to aheader structure on the cardiac stimulator and is implanted distally atone or more sites within the heart requiring cardiac stimulation orsensing. The cardiac stimulator is normally a pacemaker, acardioverter/defibrillator, a sensing instrument, or some combination ofthese devices.

At the time of implantation, the distal end of a cardiac lead isinserted through an incision in the chest and manipulated by thephysician to the site requiring electrical stimulation with the aid of aflexible stylet that is removed prior to closure. At the site requiringelectrical stimulation, the distal end of the lead is anchored to theendocardium by an active mechanism, such as a screw-in electrode tip, oralternatively, by a passive mechanism, such as one or more radiallyspaced tines that engage the endocardium. The proximal end of the leadis then connected to the cardiac stimulator and the incision is closed.The implantation route and site are usually imaged in real time byfluoroscopy to confirm proper manipulation and placement of the lead.

A conventional cardiac stimulator lead normally consists of an elongatedflexible tubular, electrically insulating sleeve that is connectedproximally to a connector that is adapted to couple to the header of acardiac stimulator, and distally to a tubular tip electrode. One or morering-type electrodes may be secured to the sleeve at various positionsalong the length of the sleeve. The proximal end of the lead sleeve isconnected to the connector by application of various biocompatibleadhesives to various portions of the connector and the sleeve. The tipelectrode ordinarily consists of a tubular structure that has anincreased diameter portion that forms an annular shoulder against whichthe distal end of the lead sleeve is abutted. The exterior surface ofthe tubular structure is normally smooth as is the interior surface ofthe distal end of the lead sleeve.

In conventional active fixation tip electrodes, engagement with theendocardium is often achieved by projecting a corkscrew from theelectrode. This is normally carried out by twisting the corkscrew. Asthe corkscrew spirals outward from the tip, the piercing point of thecorkscrew pierces the endocardium, enabling the corkscrew to be screwedinto the tissue by further twisting. The axial movement of the corkscrewrelative to the tip electrode is usually accomplished by providing theelectrode with a set of internal threads cut to match the pitch of thecoils of the corkscrew. A stylet is inserted into the lead andtemporarily coupled to the corkscrew. The stylet is twisted by hand torotate the corkscrew.

Conventional open lumen leads of both the active and passive fixationvarieties are subject to the influx of body fluids. Some fluid influx isusually expected, particularly in the period immediately followingimplantation when inflamation is most pronounced and fibrous in-growthis not established enough to provide a natural barrier to fluid flow.However, some leads are subjected to heavy influx as a result of blooddisorders such as hemophilia, unexpected and prolonged inflammation, orother causes. Heavy and/or prolonged influx may harm the lead. Tocounter the potentially deleterious effects of fluid influx,conventional open lumen leads frequently include a washer or gasketwithin the tip electrode to restrict the influx of body fluids into theleads. These gaskets are molded with a central opening of fixed diameterto accommodate the corkscrew.

There are several disadvantages associated with conventional activefixation leads. It is often difficult for the implanting physician toverify both the proper deployment of a corkscrew from the tip electrode,and the successful engagement of myocardial tissue by the corkscrew. Thedifficulty stems from the fact that past and current corkscrews are toosmall to be readily perceived via fluoroscopy. In circumstances where aconventional corkscrew fails to deploy in situ and there is no visualverification of the problem, a physician may needlessly persist intwisting a stylet in an attempt to extend the corkscrew.

In addition to presenting difficulties in detecting corkscrewdeployment, conventional leads do not provide visual verification ofendocardial penetration by the corkscrew. The problem also stems fromlimitations in X-ray imaging. As a consequence, the most common methodof verifying a proper engagement of the endocardium by the corkscrew isby touch. Following deployment of the corkscrew, the physician applies agentle, axial, tensile force on the lead connector. An absence ofappreciable longitudinal movement of the lead is an indication that thecorkscrew has successfully penetrated and engaged the tissue. However, asudden longitudinal movement of the lead is an indication that thecorkscrew either did not engage enough tissue or did not engage anytissue at all. In such circumstances, the physician must retract thecorkscrew, reposition the tip of the lead proximate the targeted tissue,and redeploy the corkscrew. This process may be very time consuming,particularly where very precise electrode positioning is medicallyindicated and the targeted tissue is difficult to reach, e.g. requirescomplex bending and manipulation of the stylet.

The problem of tissue engagement verification may be aggravated by otheraspects of conventional tip electrode and corkscrew design. In mostconventional leads, the corkscrew is deployed by a set of internalthreads in the tip electrode. The threads extend from some point withinthe electrode to the opening at the distal end of the electrode fromwhich the corkscrew deploys. A by-product of this design is that thecorkscrew deploys as soon as the stylet is twisted. This may not beproblematic where the tip is positioned and maintained in close contactwith the targeted tissue. However, if the tip is not bearing directlyagainst the targeted tissue or not positioned within a fraction of thetotal length of the corkscrew at the time the stylet is twisted, thecorkscrew may deploy and either not engage any tissue at all or onlypenetrate a small distance into the tissue. In the former situation, thecorkscrew will have to be retracted and second attempt made. In thelatter scenario, two undesirable outcomes may result. First, a less thanoptimum amount of tissue penetration may result. Second, minimal tissuepenetration by a fully extended corkscrew may result in the conductingtip of the electrode having only intermittent physical contact with thetargeted tissue or no contact at all.

As noted above, many conventional leads incorporate a washer. A drawbackassociated with conventional washer design is fixed aperture size.Where, as is often the case, the washer is coaxially located with thecorkscrew, the aperture must be made large enough to accommodate theouter diameter of the corkscrew. While such washers provide somerestriction to fluid influx, their capability in this regard is limitedby their permanently sized apertures.

The present invention is directed to overcoming or reducing the effectsof one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a cardiacstimulator lead is provided. The lead includes a connector forconnecting to a cardiac stimulator and a tubular insulating sleeve thathas a first end coupled to the connector and a second end. An electrodeis coupled to the second end and has a longitudinal bore. A washer isdisposed in the bore for restricting the influx of body fluids into thesleeve. The washer has an aperture defining a rim, and is composed of ashape-memory polymeric material deformable in situ from a temporaryshape to a permanent shape whereby the area of the aperture is reducedin situ. A conductor wire is disposed in the sleeve and coupled betweenthe connector and the electrode for transmitting electric signalsbetween the cardiac stimulator and the electrode.

In accordance with another aspect of the present invention, a cardiacstimulator lead is provided. The lead includes a connector forconnecting to a cardiac stimulator. The connector has a pin memberrotatably coupled thereto. A tubular insulating sleeve has a first endcoupled to the connector and a second end. An electrode is coupled tothe second end and has a longitudinal bore. A corkscrew is coupled tothe electrode and is projectable from and retractable into the bore. Aportion of the electrode is radiopaque. The lead includes means fortransmitting torque from the pin member to the corkscrew. A radiopaquemember is coupled to the corkscrew. A conductor wire is disposed in thesleeve and coupled between the connector and the electrode fortransmitting electric signals between the cardiac stimulator and theelectrode.

In accordance with another aspect of the present invention, an apparatusis provided. In a cardiac stimulator lead that has a tubular electrode,the apparatus includes a washer disposed in the electrode forrestricting the influx of body fluids therein. The washer has anaperture defining a rim, and is composed of a shape-memory polymericmaterial deformable in situ from a temporary shape to a permanent shapewhereby the area of the aperture is reduced in situ.

In accordance with still another aspect of the present invention, a tipelectrode for a cardiac lead is provided. The tip electrode includes atubular shank having a longitudinal bore extending therethrough. Thebore has a first longitudinal section that has at least one internalthread and a second longitudinal section. A corkscrew is disposed in thebore and has a first range of axial movement wherein the at least oneinternal thread is engaged, and a second range of axial movement whereinthe at least one internal thread is not engaged. A portion of thecorkscrew projects from the second longitudinal portion in the secondrange of axial movement. The tip includes means for rotating thecorkscrew to move the corkscrew axially while in the first range ofaxial movement and to screw the corkscrew into myocardial tissue whilein the second range of axial movement.

In accordance with another aspect of the present invention, a cardiacstimulator lead is provided. The lead includes a connector forconnecting to a cardiac stimulator and a tubular insulating sleeve thathas a first end coupled to the connector and a second end. An electrodeis coupled to the second end and has a longitudinal bore extendingtherethrough. The bore has a first longitudinal portion that has atleast one internal thread and a second longitudinal portion. A corkscrewis disposed in the bore. The corkscrew has a first range of axialmovement wherein the at least one internal thread is engaged, and asecond axial range of axial movement wherein the at least one internalthread is not engaged. A portion of the corkscrew projects from thesecond longitudinal portion in the second range of axial movement. Thelead includes means for rotating the corkscrew to move the corkscrewaxially while in the first range of axial movement and to screw thecorkscrew into myocardial tissue while in the second range of movement.A conductor wire is disposed in the sleeve and coupled between theconnector and the electrode for transmitting electric signals betweenthe cardiac stimulator and the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 is a pictorial view of an exemplary embodiment of a cardiacstimulator lead and a cardiac stimulator in accordance with the presentinvention;

FIG. 2 is a cross-sectional view of the cardiac lead of FIG. 1 taken atsection 2—2 in accordance with the present invention;

FIG. 3 is a close-in view of a portion of the lead shown in FIG. 2depicting the rotatable pin member in accordance with the presentinvention;

FIG. 4 is a cross-sectional view of FIGS. 2 and 3 taken at section 4—4in accordance with the present invention;

FIG. 5 is a close-in view of a portion of the lead shown in FIG. 2depicting another portion of the connector in accordance with thepresent invention;

FIG. 6 is a cross-sectional view of FIG. 1 taken at section 6—6 inaccordance with the present invention;

FIG. 7 is a close-in view of a portion of the electrode shown in FIG. 6in accordance with the present invention;

FIG. 8 is a cross-sectional view like FIG. 6 of an alternate tipelectrode embodying a “smart” corkscrew in accordance with the presentinvention;

FIG. 9 is a cross-sectional view like FIG. 7 depicting partial extensionof the “smart” corkscrew in accordance with the present invention;

FIG. 10 is a cross-sectional view like FIG. 7 depicting partialextension of the “smart” corkscrew in accordance with the presentinvention;

FIG. 11 is a cross-sectional view like FIG. 7 of a portion of a tipelectrode incorporating a washer composed of a shape-memory polymericmaterial in accordance with the present invention;

FIG. 12 is a cross-sectional view depicting in situ deformation of thewasher of FIG. 11 in accordance with the present invention;

FIG. 13 is a cross-sectional view like FIG. 11 of an alternateshape-memory washer following in situ deformation in accordance with thepresent invention;

FIG. 14 is a cross-sectional view like FIG. 11 of another alternateshape-memory washer following in situ deformation in accordance with thepresent invention;

FIG. 15 is a cross-sectional view of the washer of FIG. 14 prior to insitu deformation in accordance with the present invention; and

FIG. 16 is an end view of the washer of FIG. 15 in accordance with thepresent invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In the drawings described below, reference numerals are generallyrepeated where identical elements appear in more than one figure.Turning now to the drawings, and in particular to FIG. 1, there is shownan exemplary cardiac stimulator lead 10 that includes a flexibleinsulating sleeve 12 that has a proximal end 14 coupled to a connector16, and a distal end 18 coupled to a tip electrode 20. The connector 16is designed to be inserted into a cardiac stimulator 24, and is shownhighly exaggerated in size relative to the cardiac stimulator 24. Thecardiac stimulator 24 may be a pacemaker, a cardioverter/defibrillator,or other type of stimulator or a sensing instrument. The tip electrode20 includes a tip 25 and a corkscrew 26 projectable therefrom to engageand actively secure the lead 10 to myocardial tissue. The illustratedembodiment of the lead 10 is bipolar. Accordingly, the distal end 18 isprovided with an electrode 27 located proximal to the tip electrode 20.However, unipolar or other multi-polar arrangements are possible aswell. A suture sleeve 28 is slipped over the sleeve 12. Duringimplantation, the suture sleeve 28 is sewn to body tissue at the site oftransvenous entry.

The sleeve 12 is a flexible tubular member that provides a robust,electrically insulating coupling between the connector 16 and theelectrode 20. The sleeve 12 protects one or more fine gage conductorwires enclosed therein from body fluids and tissues, and isadvantageously composed of a biocompatible, electrically insulatingmaterial, such as silicone, polyurethane, or like materials.

The detailed structure of the connector 16 may be understood byreferring now to FIG. 2, which is a cross-sectional view of FIG. 1 takenat section 2—2. The connector 16 includes a connector pin assembly 30coupled to a connector sleeve assembly 32. For clarity of illustration,the connector pin assembly 30 and the connector sleeve assembly 32 areshown exploded. The connector pin assembly 30 includes a tubular pinmember 34 that has an elongated proximal end 36 designed to makeelectrical contact with one or more electrical contacts inside thecardiac stimulator 24 depicted in FIG. 1, and serves as a handle fortwisting the pin 34 to manipulate the corkscrew 26 as described below.The distal end of the pin 34 consists of an intermediate shank 38 thattapers down from the proximal end 36 to establish an annular shoulder37, an intermediate shank 39, and a distal shank 40. The intermediateshank 39 is suitably sized to accommodate the nested coils of aconductor wire 42 and another conductor wire 44. The distal shank 40 issized to receive the coils of a torque coil 48. The wire 42 iselectrically connected distally to the tip electrode 20 depicted in FIG.1, and the wire 44 is electrically connected distally to the annularelectrode 27 depicted in FIG. 1. The connections of the wires 42 and 44to the pin assembly 30 will be described in more detail below. A lumen46 extends through the pin member 34.

A first insulating sleeve 50 is coupled to the exterior of the pinmember 34. The first insulating sleeve 50 includes longitudinallyspaced-apart O-rings 52 and 54 that are designed to engage structureswithin the cardiac stimulator 24 shown in FIG. 1 and to provide a sealfor the pin member 34 against the intrusion of body fluids followingimplantation. A single O-ring may be used in place of the pair 52 and54. The first insulating sleeve 50 is provided with a proximally facingchamfer surface 56 that is principally designed to provide a taperedsurface to facilitate easy insertion of the connector 16 into thecardiac stimulator 24 shown in FIG. 1. The distal end of the firstinsulating sleeve 50 includes a distally facing annular surface 58against which the conductor sleeve assembly 32 is abutted when theconnector 16 is assembled. The first insulating sleeve 50 isadvantageously composed of a biocompatible flexible material that may beadvantageously injection molded around the pin member 34. The materialmay be silicone, polyurethane, or like materials. In this way, theO-rings 52 and 54 may be formed integrally with the first insulatingsleeve 50. Alternatively, the first insulating sleeve 50 may be providedwith external grooves and the O-rings 52 and 54 secured to the firstinsulating sleeve 50 as separate members.

Referring now also to FIG. 3, which is a detailed view of the portion ofFIG. 2 circumscribed by the dashed oval 60, and to FIG. 4, which is across-sectional view of FIG. 3 taken at section 4—4, an annular member62 is disposed around a reduced diameter portion 64 of the sleeve 50.The annular member 62 includes a distally projecting flag 66 to whichthe conductor wire 44 is attached and which provides an electricalpathway between the wire 44 and a contact (not shown) within the cardiacstimulator 24 shown in FIG. 1. The annular member 62 includes aproximally projecting reduced diameter nipple 68 that projects into thefirst insulating sleeve 50. The nipple has two or more circumferentiallyspaced ports 70 and 72 that enable molded structure to harden thereinand provide a secure mechanical engagement between the first insulatingsleeve 50 and the annular member 62. The flag 66 is provided with anexternal circumferential groove 74 that is dimensioned to receive thestripped end 76 of the conductor wire 44. The stripped end 76 is securedto the flag 66 by laser welding or like welding techniques.

As best seen in FIG. 2, the sleeve 12 is provided with a longitudinallyextending slot 77 that is slightly wider than the outer diameter of thewire 44. The slot 77 provides a space to accommodate the wire 44 so thatthe sleeve 12 may be pushed past the wire 44 and abutted against thereduced diameter portion 64.

Electrical connection between the conductor wire 42 and the pin member34 is established by a cylindrical contact sleeve 78 through which thepin member 34 is journalled and which is disposed partially within theannular member 62. The contact sleeve 78 abuts proximally against thereduced diameter portion 64 and is provided distally with an inwardlytapering portion 80 that engages a notch in the pin member 34 at 82. Theengagement between the tapered portion 80 and the notch 82 serves toretain the pin member 34 within the connector pin assembly 30. Asdiscussed more below, the pin member 34 is rotated to extend and/orretract the corkscrew 26 depicted in FIG. 1. The skilled artisan willappreciate that if the conductor wire 42 is allowed to rotate with thepin member 34, the wire 42 may become damaged or provide undesirableresistance to the rotation of the pin member 34. Accordingly, the fitprovided between the tapered portion 80 and the notch 82 is such thatthe pin member 34 may readily be rotated relative to the fixed contactsleeve 78 while still maintaining sufficient contact between the pinmember 34 and the contact sleeve 80 such that electrical conductivitybetween the conductor wire 42 and the pin member 34 is retained. As bestseen in FIG. 4, the wire 42 is stripped at 84 and secured to the contactsleeve 78 by laser welding or like techniques. Electrical isolationbetween the annular member 62 and the contact sleeve 78 is provided byan annular bushing 86 that includes distally disposed annular flange 88shoulders against the distal end of the annular member 62. The flange isnot coextensive with the entire circumference of the bushing 86.Instead, the flange 88 includes a cutout, best seen in FIG. 4, extendingfrom the surface 90 to the surface 92. The cutout is provided toaccommodate the flag 66.

The embodiment depicted in FIGS. 1, 2, 3, and 4, is bipolar. However, aunipolar arrangement may be implemented by incorporating a singleconductor wire, such as the wire 42, that is coupled to either the pinmember 34 or to the flag 66. Similarly, the conductor wires 42 and 44are depicted as single individually insulated wires with insulationstripped prior to welding to contact sleeve 68 and the flag 66. However,the skilled artisan will appreciate that the conductor wires 42 and 44may not be individually insulated if the lead 10 is unipolar or if thevarious conductor wires in the lead 10 are coaxially arranged orarranged in a nested configuration.

Referring again specifically to FIGS. 2 and 3, the torque coil 48 issecured to the distal shank 40 by laser welding or like weldingtechniques. The pitch of the individual coils in the torque coil 48 islargely a matter of design discretion. The skilled artisan willappreciate that as the pitch of the coils is increased, the torquecarrying capabilities of the coil 48 will decrease unless the stiffnessof the material used to fabricate the coil 48 is proportionallyincreased. The torque coil 48 is advantageously composed of abiocompatible material with sufficient stiffness to readily transmittorque from the pin member 34 to the corkscrew 26 depicted in FIG. 1.Exemplary materials include MP35N alloy, 316L stainless steel, or likematerials. The torque coil 48 and the wires 42 and 44 extendlongitudinally through the lumen 93 of the sleeve 12 to the tipelectrode 20.

It is desirable to electrically isolate the annular member 62 from thepin member 34 to alleviate the potential for short circuiting. This isparticularly important during electrical verification testing, which isnormally done at relatively high voltage. The primary electricalinsulation is provided by the first insulating sleeve 50, andparticularly the reduced diameter portion 64, as well as the bushing 86.It is anticipated that the material used to fabricate the firstinsulating sleeve 50 will readily fill the space, and provide a completeelectrically insulating separation between the annular member 62 and thepin member 34. However, the skilled artisan will appreciate that thereis the possibility of void formation during the molding process due toair bubbles or other mechanisms. If a void is formed in the reduceddiameter portion 64 between the annular member 62 and the pin member 34,destructive arcing may occur in the void during high voltage electricalverification testing of the lead 10. To reduce the possibility of shortsthrough a void formed in the reduced diameter portion 64, an insulatingannular member 94 may be slipped over the intermediate shank 38 andabutted proximally against the shoulder 37 prior to molding, of thefirst insulating sleeve 50. The insulating annular member 94 may becomposed of a variety of biocompatible insulating materials such as, forexample, polyimide, polyurethane, or like materials.

Referring again to FIG. 2, the connector sleeve assembly 32 includes aconductor sleeve 96 that is coupled to a second insulating sleeve 98.The second insulating sleeve 98 is a tubular member of such length andthe scale of FIG. 2 is such that the second insulating sleeve 98 isshown broken. The conductor sleeve 96 includes a proximally disposedbore 100 that is dimensioned so that the conductor sleeve 96 may bereadily slipped over the annular member 62 until the annular surface 102of the conductor sleeve 96 abuts the annular shoulder 58 of the firstinsulating sleeve 50. The conductor sleeve 96 is designed to establishan electrical pathway between the annular member 62 and a conductingstructure inside the cardiac stimulator 24 shown in FIG. 1. Accordingly,the fit between the internal diameter of the conductor sleeve 96 and theouter diameter of the annular member 62 should be close enough toprovide good electrical contact. The conductor sleeve 96 is coupled tothe annular member 62 by laser welding or like techniques.

The proximal end 103 of the second insulating sleeve 98 is provided withtwo longitudinally spaced-apart O-rings 104 and 106 that serve to sealthe conductor sleeve 96 against the intrusion of body fluids after thelead 10 is coupled to the cardiac stimulator 24 shown in FIG. 1. As withthe aforementioned O-rings 52 and 54, the O-rings 104 and 106 may beintegrally molded into the second insulating sleeve 98 or attached asseparate members. On the distal side of the O-ring 106, the secondinsulating sleeve 98 expands in diameter and defines a chamfer surface108 that provides the same functionality as the chamfer surface 56,albeit in conjunction with a different portion of the internal structureof the cardiac stimulator 24 shown in FIG. 1. The internal diameter ofthe second insulating sleeve 98 is generally dimensioned to provide asliding fit with the outer surface of the sleeve 12 to permit easyassembly. The second insulating sleeve 98 is secured to the sleeve 12 bya suitable biocompatible medical grade adhesive, such as silicone, orany of a variety of two stage adhesives. To facilitate the introductionand spreading of the adhesive, the second insulating sleeve 98 isprovided with a port 110. Adhesive is introduced into the port 110 underslight pressure to encourage the rapid and uniform spreading of theadhesive around the sleeve 12. The flow characteristics of the adhesivemay be enhanced by thinning with a suitable diluent, such as heptane,prior to injection through the port 110. In addition, adhesive is backfilled between the second insulating sleeve 98 and the sleeve 12 byinjection under slight pressure at the interface designated 112.

The connection between the conductor sleeve 96 and the second insulatingsleeve 98 may be more readily understood by referring now to FIG. 5,which is a magnified view of the portion of FIG. 2 circumscribed by thedashed oval 114. Note that in FIG. 5, the sleeve 12 is not shown forclarity of illustration. A central portion 116 of the conductor sleeve96 is provided with a plurality of circumferentially spaced bores, sixof which are depicted at 118, 120, 122, 124, 126, and 128. The bores118, 120, 122, 124, 126, and 128 are designed to enable the materialused to mold the second insulating sleeve 98 to flow into the bores 118,129, 122, 124, 126, and 128 and harden into buttons 130, 132, 134, 136,138, and 140. The engagement between the buttons 130, 132, 134, 136,138, and 140 and the central portion 116 of the conductor sleeve 96establishes a secure mechanical engagement between the conductor sleeve96 and the second insulating sleeve 98. The second insulating sleeve 98is advantageously composed of the same types of materials used tofabricate the first insulating sleeve 50 shown in FIG. 2, and isadvantageously injection molded.

The pin member 34, the annular member 62, and the conductor sleeve 96are advantageously composed of a biocompatible conducting material thatmay be welded via laser or like techniques. Exemplary materials include316L stainless steel, other suitable types of stainless steel, MP35N, orlike materials.

The connector 16 depicted in FIGS. 1, 2, 3, 4, and 5, eliminates thenecessity for the conventionally used tubular crimping members and theattendant difficulties in establishing consistent and reliable crimpedconnections between the conductor wires of the lead and the variouscrimping members. Reliable electrical and mechanical connection betweenthe conductor wires 42 and 44 and the connector 16 are established bywelding. The use of welded connections in lieu of crimping tubes orslugs permits interim inspection and testing of the wire-to-connectorconnections and more rapid assembly.

The detailed structure of the tip electrode 20 may be understood byreferring now to FIG. 6, which is a cross-sectional view of FIG. 1 takenat section 6—6, and to FIG. 7, which is a detailed view of a portion ofFIG. 6. The electrode 20 consists of a tubular shank 141 coupled toanother tubular shank 142 and sharing a common, centrally disposed bore143. The shank 141 includes a proximally disposed flange 144 and adistally positioned flange 145. The flange 145 abuts the proximal end146 of the shank 142, and terminates short of the distal end of theshank 141 so that a distally facing annular shoulder 147 projects intothe shank 142. Alternatively, the structure of the shanks 141 and 142may be incorporated into a single piece.

The distal coils 148 of the conductor wire 42 are spiraled around theshank 141 so that at lease one coil 148 is disposed between the flange144 and the flange 145. This provides a mechanical capture of the coilor coils 148 to secure the wire 42 to the shank 141. The wire 42 isstripped distally to establish a conductive path to the shank 141. Thewire 42 may also be secured by laser welding, other like weldingtechniques, or other suitable fastening methods. The main body of theshank 141 is provided with an outer diameter that is slightly largerthan the inner diameter of the coils 148 of the wire 42, but smallerthan that of the flanges 144 and 145. The distal coils 148 may beconnected to the shank 141 by first urging the coils 148 over the mainbody of the shank 144 and then over the flange 144, and finally bywelding, if desired.

The shank 142 is provided with a set of internal grooves or threads 150dimensioned to receive the corkscrew 26, which is shown in a partiallyextended position in FIG. 6. The corkscrew 26 is connected proximally tothe torque coil 48 at 152 by laser welding or like techniques. Rotationof the torque coil 48 causes the corkscrew 26 to rotate. As thecorkscrew 26 rotates, the threads 150 urge the corkscrew 26 to extendfrom or retract into the bore 143, depending on the direction ofrotation and the type of threads, i.e., left or right handed. The numberof threads is a matter of discretion.

An annular washer 156 having a central aperture 158 is disposed insidethe shank 142 and abutted against the annular shoulder 147 of the shank141. The washer 156 is designed to provide some restriction to theinflux of body fluids into the lumen 93 of the sleeve 12. The washer 156may be composed of a variety of biocompatible flexible materials, suchas, silicone, polyimide, or like materials. The aperture 158 is providedand sized to accommodate the torque coil 48.

The shanks 141 and 142 are inserted into the distal end 18 of the sleeve12. The tip 25 of the shank 142 is provided with an expanded diameter toestablish a proximally facing annular shoulder 159 against which thedistal end 18 is abutted. To secure the electrode 20 to the sleeve 12, abiocompatible adhesive is applied to the exterior of the shanks 141 and142 prior to insertion into the distal end 18 of the sleeve 12. Theadhesive may be a suitable medical grade adhesive, such as siliconebased adhesive, a two-part adhesive, or similar adhesives. Theelectrical transmission capability of the tip 25 is enhanced byincreasing the surface thereof exposed to myocardial tissue. In thisregard, one or more slots 160 are provided in the face of the tip 25.

The shank 142 may be fabricated from a variety of biocompatibleconducting materials, such as iridium oxide coated titanium, MP35N,stainless steel, platinum-iridium alloy consisting of approximately 90%platinum and 10% iridium, or some other biocompatible conducting metal,or a semiconductor material, such as silicon, or other semiconductormaterial.

It is desirable for the implanting physician to be able to readilyverify deployment of the corkscrew 26 during implantation. Inconventional lead designs, this task is often difficult due to the lackof radiopacity of conventional corkscrews. To alleviate this difficulty,a portion of the electrode 20 is composed of a suitable biocompatibleradiopaque material, such as, platinum iridium alloy (90% platinum, 10%iridium, or other suitable radiopaque material. In this example, theshank 141 is composed of radiopaque material. The shank 141 thusprovides a radiopaque marker of fixed position, that is, fixed relativeto the sleeve 12 and the electrode 20, and as such, serves as a positionbenchmark. In addition, a radiopaque member or slug 161 is coupled tothe torque coil 48, and thus to the corkscrew, by nesting the slug 161inside the coil 48 as shown, or by making the slug 161 tubular andnesting it around the torque coil 48. In the embodiment illustrated inFIG. 6, the slug 161 consists of a cylindrical member having a radiallyoutwardly projecting flange 162 that is disposed between adjacent coilsof the torque coil 48 and provides a means of preventing the slug 161from moving axially independently of the coils 48. If desired, the slug161 may also be welded to the torque coil 48.

Prior to manipulation of the torque coil 48 to extend or retract thecorkscrew 26, the initial axial separation of the slug 161 and the shank141 may be readily determined via fluoroscopy. During extension orretraction, the torque coil 48 is rotated resulting in an axial movementof the corkscrew 26, and both the torque coil 48 and the slug 161 whilethe shank 141 remains fixed. The change in axial spacing between theslug 161 and the shank 141 may be easily observed under fluoroscopy.Thus, a ready method of quickly verifying the extension and/or theretraction of the corkscrew 26 is provided.

The extension and retraction operations of the lead 10 may be understoodby referring now to FIGS. 1, 2, and 6. The lead 10 is implantedendocardially and the electrode 20 is positioned proximate the targetedmyocardial tissue, typically by using a stylet (not shown) that isinserted through the pin member 34 and advanced down the lumen 93 of thesleeve 12. Through a combination of axial force applied on the proximalend of the lead 10 and manipulation of the stylet, the tip 25 is broughtinto physical engagement with myocardial tissue. To extend the corkscrew26 and engage the myocardial tissue, the pin member 34 is twisted byhand either clockwise or counterclockwise, depending upon whether thegrooves in the shank 144 are right-handed or left-handed. Torquetransmitted to the pin member 34 by hand is, in turn, transmitted to thecorkscrew 26 via the torque coil 48. Extension of the corkscrew 26 outof the shank 144 may be verified through fluoroscopy or other imagingtechniques by observing the movement of the radiopaque slug 161 inrelation to the shank 141. After the corkscrew 26 has been fullyextended, successful engagement with myocardial tissue may be verifiedby applying a gentle axial force to the connector by hand. Anunsuccessful fixation with myocardial tissue may be determined viaimaging as well as a sudden axial movement of the lead 10 in response tothe applied axial force. To retract the corkscrew 26, the pin member 34is twisted in the opposite direction.

In an alternate embodiment depicted in FIGS. 8, 9, and 10, the tipelectrode, now designated 20′, is provided with a “smart” corkscrew, nowdesignated 26′. The term “smart” refers to the ability of the corkscrew26′ to fully deploy only in circumstances where the corkscrew 26′ isfirmly engaging and penetrating myocardial tissue 164. FIG. 8 depictsthe electrode 20′ with the corkscrew 26′ in a fully retracted position.The electrode 20′ is a tubular member provided with a longitudinallydisposed lumen 166 that is divided into two sections, a firstlongitudinal or threaded section 168, and a second longitudinal orsmooth section 170. In the threaded section 168, the electrode 20′ isprovided with a set of internal threads or grooves 172 that areconfigured similarly or identically to the grooves 150 depicted in FIG.6. The corkscrew 26′ has a first range of axial movement while engagedby the threads 172. The number of threads 172 is a matter of designdiscretion, though at least one is necessary to move the corkscrew 26′axially.

The smooth, i.e., unthreaded, section 170 is provided with an internaldiameter that is larger than the outer diameter of the corkscrew 26′ andhas a relatively smooth bore to enable the corkscrew 26′ to passtherethrough with little or no interference. The corkscrew 26′ has asecond range of axial movement where the threads 172 are not engaged.

The torque coil 48 is coupled proximally to the corkscrew 26′ asdescribed above. If a portion of the corkscrew 26′ is in physicalengagement with the grooves 172, as is the case in FIG. 8, torqueapplied to the corkscrew 26′ via the torque coil 48 will produce anaxial movement of the corkscrew 26′ as generally described above.

The operation of this embodiment may be understood by referring now toFIGS. 9 and 10. The electrode 20′ is implanted and positioned proximatemyocardial tissue 164 generally as described above. Through manipulationof the torque coil 48, the corkscrew 26′ is moved axially through thefirst range of axial movement from the fully retracted position depictedin FIG. 8 to the partially extended position shown in FIG. 9. In thepartially extended position shown in FIG. 9, the corkscrew 26′ has movedaxially so that no portion of the corkscrew 26′ is in physicalengagement with the grooves 172. At this stage, the corkscrew 26′ is inthe second range of axial movement, and continued twisting of the torquecoil 48 will simply rotate the corkscrew 26′ and will not appreciablyadvance the corkscrew 26′ axially. However, as shown in FIG. 10, whenthe electrode 20′ is brought into physical contact with the myocardialtissue 164, further twisting of the torque coil 48 will result in thecorkscrew 26′ engaging and penetrating the myocardial tissue 164axially. In this way, the corkscrew 26′ will only project significantlyfrom the electrode 20′ when the corkscrew 26′ is in physical engagementwith myocardial tissue 164. The electrode 20′ eliminates the timeconsuming task of retracting the corkscrew 26′ into the electrode 20′ bytwisting the torque coil 48 in circumstances where the corkscrew 26′ didnot successfully engage the myocardial tissue 164 and where anotherattempt to attach the electrode 20′ to the myocardial tissue iscontemplated.

FIGS. 11, 12, and 13 are views of scope similar to FIG. 7, but depictalternate embodiments incorporating a washer composed of a heatsensitive shape-memory polymeric material. In the embodiment depicted inFIGS. 11 and 12, the washer is designated 256. In the embodiment shownin FIG. 13, the washer is designated 356. A heat-sensitive shape-memorypolymeric material behaves generally like a rigid material while attemperatures below the glass transition temperature T_(g), but undergoessignificant softening and may be readily plastically deformed whenheated above T_(g). When the material is then cooled below T_(g), thedeformation is fixed and the shape remains stable. However, the originalshape of the material may be recovered by reheating the material aboveT_(g).

Turning initially to FIGS. 11 and 12, the washer 256 is first moldedinto the permanent shape shown in FIG. 12 during production. The washer256 is advantageously molded with an aperture 174 that has a permanentinner diameter that will significantly restrict the influx of bodyfluids. The aperture defines a rim 175. A variety of well known moldingtechniques may be used to create the washer 256, such as injectionmolding, extrusion molding, or like techniques. The molding processsubjects the heat-sensitive shape-memory polymeric material to atemperature well in excess of the T_(g) for the material for asufficient time to form the washer 256 into the permanent shape.Thereafter, the washer 256 may be deformed into the temporary shapeshown in FIG. 11 by deforming the washer 256 at a temperature aboveT_(g), and maintaining the washer 256 in the temporary shape while thetemperature is lowered below T_(g). After cooling below T_(g), thewasher 256 retains the temporary shape. However, if the washer 256 islater heated above T_(g), it will deform substantially back into thepermanent shape in which it was originally molded. In this way, thewasher 256 may be initially produced with a permanent shape that has avery small inner diameter aperture 174.

Where molding of the desired permanent shape is difficult in view of themolding process used and the small dimensions of the washer 256, thewasher 256 may be molded with a first permanent shape that best suitsthe molding process. This may be, for example, a shape with a largerthan desired permanent diameter. Thereafter, the washer 256 may beprovided with a new permanent shape by heating the washer 256 aboveT_(g), deforming the washer 256 into a new desired permanent shape,(e.g. a shape with a more suitable permanent diameter) and maintainingthe washer 145′ in that shape and at that temperature for a selectedperiod of time. The heating time required to set the new permanent shapewill depend on the particular polymer.

In FIGS. 11 and 12, the washer 256 is initially fabricated with apermanent shape such that the washer 256 has a relatively small diameteraperture 174 as shown in FIG. 12. Prior to insertion into the electrode20, the washer 256 is heated above the glass transition temperature forthe material used to fabricate the washer 256 and the washer 256 ismechanically deformed into the temporary shape shown in FIG. 11 so thatthe aperture 174 is large enough to readily accommodate the coils of thetorque coil 48. After the electrode 20 has been secured to myocardialtissue, the washer 256 may be again heated above the glass transitiontemperature in situ so that the washer 256 returns to its permanentshape as shown in FIG. 12. The area of the aperture 174 decreases aftertransformation into the permanent shape.

Heating the washer 256 above the glass transition temperature may beaccomplished by introducing a heated fluid into the bore 143, such assaline. It is anticipated that the permanent inner diameter of theaperture 174 may be fabricated small enough so that surface tensioneffects will restrict most if not all influx of body fluids past thewasher 256.

FIG. 13 illustrates another variation of the shape memory concept forthe washer, now designated 356. In this embodiment, the washer 356 isfabricated with a permanent shape as shown in FIG. 13. However, prior toinsertion into the electrode 20, the washer 145″ is heated above theglass transition temperature and mechanically deformed into a moreconventional shape, such as shown in FIG. 11. Subsequent to fixation tomyocardial tissue, the washer 356 may be heated above the glasstransition temperature so that the washer 356 returns to the permanentshape as shown in FIG. 13, and thereby provides a much greaterrestriction to the influx of body fluids past the washer 356.

FIGS. 14, 15, and 16 illustrate another variation of the shape-memoryconcept for the washer, now designated 456, suitable for use with anelectrode-corkscrew combination where the corkscrew is not physicallyengaged to the electrode following deployment, such as the “smart”corkscrew 26′ embodiment depicted in FIGS. 8, 9, and 10. In thisembodiment, the washer 456 is fabricated with the permanent shape shownin FIG. 14. FIGS. 15 and 16 depict cross-sectional and end views of thewasher 456 deformed into a temporary shape. Referring to FIGS. 15 and16, the washer 456 is fabricated as a conical-like structure with aplurality of peripherally spaced slots 176 that divide the washer 456into four collet-like fingers 178. Each finger 178 has a radiallyinwardly facing rim 180 that is designed to engage a coil of thecorkscrew 26, such as the coil 182. Prior to insertion into theelectrode 20, the washer 456 is deformed into the temporary shape andsecured to the shank 141 at 184 by a suitable medical grade adhesive ofthe types described above.

Following deployment of the corkscrew 26′, the washer 456 is heated insitu above the glass transition temperature T_(g), causing the washer456 to deform back into the permanent shape shown in FIG. 14. As thefingers 178 curl inward, the rims 180 engage the coil 182 and exert aproximally oriented axial load. Since the washer 456 is secured to theshank 141, the effect of the proximally oriented axial load on thecorkscrew 26′ is an axial thrust applied to the electrode 20 in theopposite direction, that is, a force that urges the electrode to moveaxially relative to the corkscrew 26 in the direction of the arrow 186shown in FIG. 14. As a result, the electrode 20 is thrust against themyocardial tissue, providing reliable contact between the electrode 20′and the targeted tissue. Note that the thrusting action of the washer456 could be accomplished by eliminating the slots 176 so that the rims180 are integral.

For long-term implantation, the washers 256, 356, and 456 may befabricated from heat-sensitive shape memory polymers such aspolynorbornene supplied by Nippon Zeon of Japan, polyurethane suppliedby Mitsubishi Heavy Industries of Japan, Calo.Mer™ supplied by PolymerTechnology Group of California, or similar materials. If the lead 10 isdesigned for more transient implantation, materials such as polyvinylchloride, or similar materials may be used in addition to theabove-described materials.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

What is claimed is:
 1. A cardiac stimulator lead, comprising: aconnector for connecting to a cardiac stimulator; a tubular insulatingsleeve having a first end coupled to the connector and a second end; anelectrode coupled to the second end and having a longitudinal bore; awasher disposed in the bore for restricting the influx of body fluidsinto the sleeve, the washer having an aperture defining a rim, thewasher being composed of a shape-memory polymeric material deformable insitu from a temporary shape to a permanent shape whereby the area of theaperture is reduced in situ; and a conductor wire disposed in the sleeveand coupled between the connector and the electrode for transmittingelectric signals between the cardiac stimulator and the electrode. 2.The cardiac stimulator lead of claim 1, comprising a corkscrew coupledto the lead and being projectable from the bore.
 3. The cardiacstimulator lead of claim 2, wherein the rim moves proximally and engagesthe corkscrew during in situ deformation, the proximal movement andengagement with the corkscrew imparting an axial load on the corkscrewto urge the electrode to move distally relative to the corkscrew.
 4. Thecardiac stimulator lead of claim 1, comprising a pin a member rotatablycoupled to the connector and a coiled wire coupled between the pinmember and the corkscrew, the pin member being rotatable to rotate thecoiled wire and the corkscrew to project the corkscrew from theelectrode.
 5. The cardiac stimulator lead of claim 1, wherein theshape-memory polymeric material comprises polynorbornene.
 6. The cardiacstimulator lead of claim 1, wherein the shape-memory polymeric materialcomprises polynorbornene.
 7. In a cardiac stimulator lead having atubular electrode, an apparatus, comprising: a washer disposed in theelectrode for restricting the influx of body fluids therein, the washerhaving an aperture defining a rim, the washer being composed of ashape-memory polymeric material deformable in situ from a temporaryshape to a permanent shape whereby the area of the aperture is reducedin situ.
 8. The apparatus of claim 7, wherein the washer has a pluralityof distally projecting collet fingers, the plurality of collect fingersmove proximally during in situ deformation.
 9. A cardiac lead,comprising: a connector; a tubular insulating sleeve having a first endand a second end, the first end coupled to the connector; an electrodehaving a longitudinal bore, the electrode coupled to the tubularinsulating sleeve second end; a conductor wire disposed in the tubularinsulating sleeve and coupled to the connector and the electrode; and awasher disposed in the longitudinal bore, the washer adapted to restrictan influx of body fluids into the tubular insulating sleeve, the washerhaving an aperture defining a rim, the washer composed of a shape-memorypolymeric material, the washer adapted to deform in situ from atemporary shape to a permanent shape.
 10. The cardiac lead of claim 9,wherein the shape-memory polymeric material comprises polynorbornene.11. The cardiac lead of claim 9, the washer further comprising aplurality of collet fingers, each projecting distally from theconnector, the collet fingers adapted to curl toward one another duringin situ deformation of the washer back to the permanent shape.
 12. Thecardiac lead of claim 9, the aperture adapted to decrease during in situdeformation of the washer back to the permanent shape.
 13. The cardiaclead of claim 9, wherein the washer has a height defining a longitudinaldimension, the washer adapted to increase in height during in situdeformation of the washer back to the permanent shape.
 14. The cardiaclead of claim 9, further comprising a corkscrew disposed in thelongitudinal bore of the electrode, the corkscrew disposed in theaperture of the washer and is projectable from and retractable into thelongitudinal bore of the electrode.
 15. The cardiac lead of claim 14,the rim adapted to engage the corkscrew and urge the electrode to movedistally relative to the corkscrew during in situ deformation of thewasher back to the permanent shape.
 16. The cardiac lead of claim 14,wherein the rim is adapted to engage the corkscrew during in situdeformation of the washer back to the permanent shape.
 17. The cardiaclead of claim 14, wherein the rim is adapted to not engage the corkscrewwhile the washer is in the temporary shape.
 18. The cardiac lead ofclaim 17, wherein the rim further comprises a plurality of radial slitsforming a plurality of collet fingers, the plurality of collet fingersadapted to engage the corkscrew during in situ deformation of the washerback to the permanent shape.
 19. The cardiac lead of claim 14, whereinthe washer has a height defining a longitudinal dimension, the washeradapted to increase in height during in situ deformation of the washerback to the permanent shape.
 20. A cardiac lead, comprising: a connectoradapted to connect to a cardiac stimulator, the connector having a pinmember rotatably coupled thereto; a tubular insulating sleeve having afirst end and a second end, the first end coupled to the connector; anelectrode having a longitudinal bore, the electrode coupled to thetubular insulating sleeve second end; a corkscrew coupled to theelectrode and projectable from and retractable into the longitudinalbore; a rotation device coupled between the pin member and thecorkscrew; a conductor wire disposed in the sleeve and coupled betweenthe connector and the electrode, the conductor wire adapted to transmitelectric signals between the cardiac stimulator and the electrode; and awasher disposed in the bore, the washer adapted to restrict an influx ofbody fluids into the sleeve, the washer having an aperture and iscomposed of a shape-memory polymeric material, the washer adapted todeform in situ from a temporary shape to a permanent shape, wherein theaperture is reduced during in situ deformation of the washer back to thepermanent shape.
 21. The cardiac lead of claim 20, wherein theshape-memory polymeric material is heat sensitive, the shape-memorypolymeric material selected from the group consisting of polynorbornene,polyurethane, and polyvinyl chloride.
 22. The cardiac lead of claim 20,wherein the corkscrew is disposed through the aperture, the rim adaptedto engage the corkscrew during in situ deformation of the washer back tothe permanent shape.
 23. The cardiac lead of claim 22, the rim adaptedto engage the corkscrew and urge the electrode to move distally relativeto the corkscrew during in situ deformation of the washer back to thepermanent shape.
 24. The cardiac lead of claim 22, wherein the rimfurther comprises a plurality of radial slits forming a plurality ofcollet fingers, the plurality of collet fingers adapted to engage thecorkscrew during in situ deformation of the washer back to the permanentshape.
 25. The cardiac lead of claim 22, wherein the washer has a heightdefining a longitudinal dimension, the washer adapted to increase inheight during in situ deformation of the washer back to the permanentshape.
 26. The cardiac lead of claim 22, the washer having a temporaryshape and a permanent shape, the temporary shape adapted such that therim does not engage the corkscrew, and the permanent shape adapted suchthat the rim engages the corkscrew during in situ deformation of thewasher from the temporary shape to the permanent shape.
 27. The cardiaclead of claim 20, wherein the rotation device is a torque coil, thetorque coil is disposed through the aperture, the rim adapted to engagethe torque coil during in situ deformation of the washer back to thepermanent shape.
 28. The cardiac lead of claim 27, the rim adapted toengage the torque coil and urge the electrode to move distally relativeto the torque coil during in situ deformation of the washer back to thepermanent shape.
 29. The cardiac lead of claim 27, wherein the rimfurther comprises a plurality of radial slits forming a plurality ofcollet fingers, the plurality of collet fingers adapted to engage thetorque coil during in situ deformation of the washer back to thepermanent shape.
 30. The cardiac lead of claim 27, wherein the washerhas a height defining a longitudinal dimension, the washer adapted toincrease in height during in situ deformation of the washer back to thepermanent shape.
 31. The cardiac lead of claim 27, the washer having atemporary shape and a permanent shape, the temporary shape adapted suchthat the rim does not engage the torque coil, and the permanent shapeadapted such that the rim engages the torque coil during in situdeformation of the washer from the temporary shape to the permanentshape.
 32. An apparatus for a cardiac lead, the apparatus comprising: atubular electrode adapted to be coupled with the cardiac lead; and awasher disposed in the tubular electrode, the washer adapted to restrictthe influx of body fluids therein, the washer having an aperturedefining a rim and composed of shape-memory polymeric material, thewasher adapted to deform in situ from a temporary shape to a permanentshape.
 33. The apparatus of claim 32, wherein the shape-memory polymericmaterial is polynorbornene.
 34. The apparatus of claim 32, the apertureadapted to decrease during in situ deformation of the washer back to thepermanent shape.
 35. The apparatus of claim 32, wherein the washer has aheight defining a longitudinal dimension, the washer adapted to increasein height during in situ deformation of the washer back to the permanentshape.
 36. A method for implanting a cardiac stimulator lead, the methodcomprising: slidably passing a stimulator lead through vasculature, thelead comprising: a connector adapted to connect to a cardiac stimulator;a pin member rotatably coupled to the connector; a tubular insulatingsleeve having a first end and a second end, the first end coupled to theconnector; an electrode having a longitudinal bore, the electrodecoupled to the tubular insulating sleeve second end; a conductor wiredisposed in the tubular insulating sleeve and coupled to the connectorand the electrode; a washer disposed in the longitudinal bore, thewasher adapted to restrict an influx of body fluids into the tubularinsulating sleeve, the washer having an aperture defining a rim, thewasher composed of a shape-memory polymeric material, the washer adaptedto deform in situ from a temporary shape to a permanent shape; acorkscrew disposed in the longitudinal bore of the electrode, thecorkscrew disposed in the aperture of the washer and is projectable fromand retractable into the longitudinal bore of the electrode; and arotation device coupled to the corkscrew and the pin member; abuttingthe electrode against cardiac tissue; rotating the rotation devicewherein the corkscrew is rotated and urged axially out of the bore andengaging cardiac tissue; and heating the washer and deforming the washerin situ from a temporary shape to a permanent shape.
 37. The method ofclaim 36, further comprising engaging the corkscrew with the rim whilethe washer is in the permanent shape, where the rim does not engage thecorkscrew while the washer is in the temporary shape.
 38. A method forimplanting a cardiac stimulator lead, the method comprising: slidablypassing a stimulator lead through vasculature, the lead comprising: aconnector adapted to connect to a cardiac stimulator; a pin memberrotatably coupled to the connector; a tubular insulating sleeve having afirst end and a second end, the first end coupled to the connector; anelectrode having a longitudinal bore, the electrode coupled to thetubular insulating sleeve second end; a conductor wire disposed in thetubular insulating sleeve and coupled to the connector and theelectrode; and a washer disposed in the longitudinal bore, the washeradapted to restrict an influx of body fluids into the tubular insulatingsleeve, the washer having an aperture defining a rim, the washercomposed of a shape-memory polymeric material, the washer adapted todeform in situ from a temporary shape to a permanent shape, the washerfurther comprising a plurality of peripherally spaced slots that dividethe rim into a plurality of collet fingers, each projecting distallyfrom the connector, the collet fingers adapted to curl toward oneanother during in situ deformation of the washer back to the permanentshape; a corkscrew disposed in the longitudinal bore of the electrode,the corkscrew disposed in the aperture of the washer and is projectablefrom and retractable into the longitudinal bore of the electrode, theplurality of collet fingers having a radially inwardly facing rimadapted to engage the corkscrew when the washer deforms in situ from atemporary shape to a permanent shape; a rotation device coupled to thecorkscrew and the pin member; abutting the electrode against cardiactissue; rotating the rotation device wherein the corkscrew is rotatedand urged axially out of the bore and engaging cardiac tissue; andheating the washer and deforming the washer in situ from a temporaryshape to a permanent shape.
 39. The method of claim 38, furthercomprising engaging the corkscrew with the collet fingers while thewasher is in the permanent shape, where the collet fingers do not engagethe corkscrew while the washer is in the temporary shape.
 40. The methodof claim 39, wherein the engaging the corkscrew with the collet fingerswhile the washer is in the permanent shape further comprises the colletfingers applying an axial load on the electrode urging the electrodeaxially in tighter engagement with the cardiac tissue.
 41. The method ofclaim 39, wherein the engaging the corkscrew with the collet fingerswhile the washer is in the permanent shape further comprises urging theelectrode to move distally relative to the corkscrew and urging theelectrode in tighter engagement with the cardiac tissue.